Hawaii and Pacific Ocean

The Pacific Ocean forms the largest volcanic region in this book, but has the smallest total land area. Region 13 covered only 'Hawaii' upon publication of the 1955 CAVW catalog. By the time of our 1981 book, it was clear that there was Holocene activity elsewhere in the Pacific and, in keeping with the original CAVW designations for both Atlantic and Indian oceans, we expanded this region to cover the full ocean basin not already covered by other catalogs (e.g. Galápagos, Chilean, and Mexican islands). Easter Island was included in this region in our 2nd edition, but has been moved since to be part of Chile's island volcanoes in subregion 1506.

Tahiti was discovered in 1767, 11 years before Captain Cook first sighted Hawaii, the most visibly volcanic part of the region. American missionaries arrived in Honolulu in 1820, and the Wilkes Expedition, with 27-yr-old J.D. Dana, arrived in Hawaii in 1840. In 1874, US troops landed in the islands, and in 1893 the Kingdom of Hawaii was overthrown by US Marines. Hawaii was annexed in 1898, ceded itself to the US as the Republic of Hawaii two years later, and became the 50th US state in 1959. In 1911, American volcanologists Perret & Shepherd started the first continuous monitoring of Kilauea, and the Hawaiian Volcano Observatory (HVO) was founded in the next year under the direction of the redoubtable Thomas Jaggar. In 1925 the Observatory came under the administration of the US Geological Survey, and the same year marked the first issue of Volcano Letter, an irregular periodical that carried news and volcano commentary from around the world until publication ceased in 1955. HVO has pioneered many approaches to monitoring of active volcanoes, and been instrumental in advancing understanding of ocean island volcanism.

Dominated by the fluid lavas of Hawaii, this region leads the world in eruptions producing lava flows, lava lakes, and radial fissure eruptions (in percentages of both its own total eruptions and those of each characteristic). The region is unusually homogeneous in its products, with virtually all eruptions consisting of basalt, from hotspot (Hawaii, Tahiti, Macdonald), ocean ridge crest, or fracture zone settings. Less than one-fifths of the eruptions in the Pacific Region display any explosive activity, and only 6% are strictly explosive, with no associated effusive activity; these are by far the lowest proportions of any region. This region has the highest proportion of submarine volcanoes (79%), and matches Africa and Arabia/Indian Ocean in having the fewest documented large explosive (VEI ?4). The obvious focus on the dramatic effusive activity can be misleading, however, as Smithsonian and USGS volcanologists have recently documented a surprisingly high number of moderate-to-large explosive eruptions from Kilauea volcano.
A surge of interest in deep-sea volcanism has increased understanding of mid-ocean rift volcanism and documented several new eruptions. Evidence for a very recent, possibly ongoing eruption was detected during a series of dives in the submersible vessel Alvin in 1991 on the East Pacific Rise at about 9° 50' N. Hot-vent animal communities that had been documented during November to December 1989 imaging were observed to have been buried by fresh basaltic lava flows, and the scorched soft tissues of partially buried biota had not yet attracted bottom scavengers. Fresh black smoker chimneys were draped by new lava flows. This position was at a depth of about 2500 m south of the Clipperton fracture zone, about 1000 km SW of Acapulco, México. It coincided with a location where fresh lava flows previously estimated as less than roughly 50 years in age had been found; later Uranium-series dating extended the eruptive record here back 7000 years. Preliminary radiometric dating using 210Pb techniques dated lava flows erupted along the East Pacific Rise at between late summer 2005 and January 2006, and a research expedition in April 2006 discovered that seismometers emplaced since 2003 had been buried by new lava flows. Further north, along the Juan de Fuca and North Gorda ridges off the coasts of Oregon and Washington, several eruptions were documented during the 1980s and 1990s by scientists of the NOAA Vents Program. These dramatic eruptions are evidence of the highly active mid-ocean ridge volcanism, but they only hint at the frequency of sea-floor volcanism. We have not included 'zero-age' volcanoes unless they have specifically dated eruptions, and the volcanoes listed here are only a small fraction of the Holocene eruptive record in this active tectonic setting.